Electrophotographic material

ABSTRACT

AN ELECTROPHOTOGRAPHIC MATERIAL IS PROVED HEREIN WHICH COMPRISES A CONDUCTIVE SUPPORT LAYER AND A PHOTOCONDUCTIVE INSULATING LAYER, THE LATTER LAYER COMPRISING A PHOTOCONDUCTIVE POLYMERIC COMPOUND SUCH AS POLY-NVINYLCARBAZOLE, AND A SENSITIZER HAVING THE FOLLOWING GENERAL FORMULA   (X&lt;((R1-)C=C(-R2)-C(=C(-R4)(-B))-(5-R3-1,2-PHENYLENE)-))+   ANION (-)   WHEREIN B REPRESENTS A RADICAL SELECTED FROM THE GROUP CONSISTING OF   2-R5,3-R6,6-R7-BENZOPYR-3-YLIUM AND X&lt;(=C(-)-C(-R8)=C(   4-(H3C-O-)PHENYL)-(1,2-PHENYLENE)-)   COMPOUNDS FALLING UNDER THE LATTER GENERAL FORMULA INCLUDE SUCH COMPOUNDS AS 2-PHENYL-4- (2&#39;&#39;-PHENYL-4&#39;&#39;-BENZOPYRANYLIDENE) BENZYL!-BENZOPYRYLIUM PERCHLORATE AND 2,3PHENYL-4- (2&#39;&#39;-PHENYL-4&#39;&#39;BENZOPYRANYLIDENE)BENZYL!-6METHYLBENZOPYRYLIUM PERCHLORATE.

Jam 23, 1973 YOSHINOBU MURAKAMI ETAL 3,7

ELECTROPHOTOGRAPHI C MATER IAL Filed March 5, 1971 3 Sheets-Sheet 1 FIG]WAVELENGTH FIG.2

WAVELENGTH (my) COMPOUND 7 FIG.3

INVENTORS YOSHINOBU MURAKAMI YO HASEGAWA KAZUHISA MORIMOTO BY Q 12ATTORNEYS J8!!- 1973 YOSHINOBU MURAKAMI ETAL 3,712,811

ELECTROPHOTOGRAPHIC MATERIAL Filed March 5, 1971 3 Sheets-Sheet 2WAVELENGTH (m u) COMPOUND 57 -FIG.5

WAVELENGTH (m COMPOUND 83 WAVELENGTH (m COMPOUND 92 INVENTORS YOSHINOBUMURAKAMI YO HASEGAWA KAZUHISA MOF?! MOj ZO' BY Mu 1%- 2M ATTORNEYS Jan.23, 1973 Filed March 5, 1971 FIG] YOSHINOBU MURAKAMI ETAL 3,712,811

ELECTROPHOTOGRAPHIC MATERIAL 3 Sheets-Sheet 3 WAVELENGTH (rn u) COMPOUND103 WAVELENGTH COMPOUND l u WAVELENGTH m l) COMPOUND 122 INVENTORSYOSHINOBU MURAKAMI YO HASEGAWA KAZUHISA MORIMOTO BY MM'EWM ATTORNEYSUnited States Patent 3,712,811 ELECTROPHOTOGRAPHIC MATERIAL YoshinobuMurakami, Osaka, Yo Hasegawa, Suita, and

Kazuhisa Morimoto, Settsu, Japan, assignors to Matsushita ElectricIndustrial Company Limited, Osaka,

Japan Filed Mar. 5, 1971, Ser. No. 121,508 Claims priority, applicationJapan, Mar. 13, 1970, 45/21,766, 45/21,767

Int. Cl. G03g 5/06 US. Cl. 961.6 3 Claims eral formula fiT V anion- LB.l;

wherein B represents a radical selected from the group consisting of andR Ru R! ACE} Compounds falling under the latter general formula includesuch compounds as2-phenyl-4-[(2-phenyl-4-benzopyranylidene)benzylJ-benzopyryliumperchlorate and 2,3- phenyl 4 [(2-phenyl-4"benzopyranylidene)benzyl]-6-methylbenzopyrylium perchlorate.

This invention relates to novel light-sensitive layers and moreparticularly to electrophotographic light-sensitive polymer layers.

V'arious light-sensitive layers are well known in theelectrophotographic art for making copies of documents, drawings,transparencies, etc. These layers contain organic photocondnctivecompounds, such as poly-N- vinylcarbazole, brominatedpoly-N-vinylcarbazoles, polyacenaphthylene, etc. These layers arenon-conductors of electricity before exposure and become electricalconductors upon exposure.

It is necessary for the electrophotographic art that the photocondnctivematerial has a high photoconductivity in the long wavelength region ofthe visible spectrum. Such a photocondnctive material makes it possiblefor the electrophotograph art to employ inexpensive and convenient lightsources such as incandescent lamps in a reduced exposure time and toreproduce colored pictures. The photoconductive materials mentionedabove, however, have usually a low photoconductivity and spectrumcharacteristics sensitive to the short wavelength region of the exposurelight and do not satisfy entirely the above requiremeat.

It is known that an addition of a so-called sensitizer can improvephotoconductivity and spectrum characteristics of the abovephotocondnctive compounds. Conventional sensitizers are dyestuifcompounds, such as triarylmethane dyes, xanthene dyes, triazine dyes oracridine dyes, but the conventional sensitizers are not entirelysatisfactory to improve the photoconductivity and the spectrumcharacteristics of the available photocondnctive compounds.

In addition to the high photoconductivity and spectrum characteristicssensitive to visible light, the electrophotographic art requires a highelectric resistance of photoconductive materials in the dark.Conventional sensitizers are apt to increase the dark conductivitywhereas they promote the photoconductivity. A high dark conductivity ofphotocondnctive materials is not desirable because it results in a lossof the applied electrostatic charge in the dark.

An object of the invention is to provide electrophotographic materialshaving a high photoconductivity and spectrum characteristics sensitiveto a long wavelength region of the visible spectrum.

Another object of the invention is to provide electrophotographicmaterials having a high electric resistance in the dark.

These and other objects are accomplished by adding a new sensitizershown hereinafter to a photocondnctive polymeric compound such aspoly-N-vinylcarbazole, brominated poly-N-vinyl-carbazole orpolyacenaphthylene, as a light-sensitive film-forming composition.

The invention is further explained in the following description withreference to the accompanying drawings wherein:

FIG. 1 represents the wedge spectrogram for an electrophotographicmaterial coated with an unsensitized solution of 10 weight percent ofbrominated poly-N-vinylcarbazole in chlorobenzene.

FIG. 2 represents the wedge spectrogram for an electrophotographicmaterial coated with a solution containing 10 weight percent ofbrominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of2-(a-phenyl-p-methoxystyryl) 4- (2'-phenyl-4'-benzopyranylidene)-methyl] benzopyrylium perchlorate, the brominated poly-N-vinylcarbazolebeing dissolved in a solvent of four weight parts of chlorobenzene andone weight part of dichloroethane.

FIG. 3 represents the wedge spectrogram for an electrophotographicmaterial coated with a solution containing 10 weight percent ofbrominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of2-styryl-3-phenyl-4- (2'-styryl-4'-benzopyranylidene methyl] -6-methylbenzopyrylium perchlorate, the brominated poly-N-vinylcarbazole beingdissolved in a solvent of four weight parts of chlorobenzene and oneweight part of dichloroethane.

FIG. 4 represents the wedge spectrogram for an electrophotographicmaterial coated with a solution containing 10 weight percent ofbrominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of2-p-methoxystyryl-4- [(2' a phenyl-p-methoxystyryl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate, the brominated poly- N-vinylcarbazolebeing dissolved. in a solvent of four weight parts of chlorobenzene andone weight part of dichloroethane.

FIG. 5 represents the wedge spectrogram for an electrophotographicmaterial coated with a solution containing 10 weight percent ofbrominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of2-p-methoxystyryl-4-[(2'- phenyl-4'-benzothiopyranylidene -rnethyl]benzopyrylium perchlorate, the brominated poly-N-vinylcarbazole beingdissolved in a solvent of four weight parts of chlorobenzene and oneweight part of dichloroethane.

FIG. 6 represents the wedge spectrogram for an electrophotographmaterial coated with a solution containing 10 weight percent ofbrominated poly-N-vinyl carbazole sensi- 3 tized with 0.04 weightpercent of 2-[2'-phenyl-4'-benzopyranylidene)methy1]3-phenylbenzopyrylium perchlorate, the brominated poly-N-vinylcarbazolebeing dissolved in a solvent of four parts of chlorobenzene and oneweight part of dichloroethane.

FIG. 7 represents the wedge spectrogram for an electrophotographicmaterial coated with a solution containing weight percent of brominatedpoly-N-vinylcarbazole sensitized with 0.04 weight percent of 2-[(4'-'benzothiopyranylidene)methyl]-3-phenylbenzopyrylium perchlorate,the brominated poly-N-vinylcarbazole being dissolved in a solvent offour weight parts of chlorobenzene and one weight part ofdichloroethane.

FIG. 8 represents the wedge spectrogram for an electrophotographicmaterial coated with a solution containing 10 weight percent ofbrominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of2-[2'-a-phenyl-pmethoxystyryl-4'-benz0pyranylidene)methyl] 3phenylbenzopyrylium perchlorate, the brominated poly-N-vinylcarbazolebeing dissolved in a solvent of four weight parts of chlorobenzene andone weight part of dichloroethane.

FIG. 9 represents the Wedge spectrogram for an electrophotographicmaterial coated with a solution containing 10 weight percent ofbrominated poly-N-vinylcarbazole sensitized with 0.04 weight percent of2-[(2'-phenyl-4'- benzothiopyranylidene)methyl]-3-phenyl benzopyryliumperchlorate, the brominated poly-N-vinylcarbazole being dissolved in asolvent of four weight parts of chlorobenzene and one weight part ofdichloroethane.

The new sensitizer, according to the present invention has the followingformula:

X Rl R3 Anionwhere B represents a radical selected from the groupconsisting of,

AGE:

R is hydrogen, phenyl or an ethenyl or an ethenyl radical selected fromthe group consisting of styryl, p-methoxystyryl, 3,4-dimethoxystyryl,m-phenylstyryl, a-phenyl-pmethoxystyryl, fl-furyl(a')ethenyl anda-phenyl-p-furyl (ot' ethenyl;

R is hydrogen or phenyl;

R is hydrogen, methyl or phenyl;

R is hydrogen or phenyl;

R is hydrogen, phenyl or an ethenyl radical selected from the groupconsisting of styryl, p-methoxystyryl, 3,4-dimethoxystyryl,a-phenyl-p-methoxystyryl, ,B-furyKa') ethenyl anda-phenyl-fi-furyl(a)ethenyl;

R is hydrogen or phenyl;

R is hydrogen, methyl or phenyl;

R is hydrogen or phenyl;

the anion is anionic function selected from the group consisting ofperchlorate, fiuoroborate, chloroferrate, chlorozincate and nitrate; and

X is oxygen or sulfur atom.

The sensitizers having the formula above mentioned are prepared by thefollowing chemical Equation A or B.

In the case of Equation A, 4-[(4-benzopyranylidene)-methyl]benzopyrylium derivative (III) is obtained by an additionreaction of 4-methoxybenzopyrylium o-nitrobenzene sulfonate (I) with abenzopyrylium salt (II) in an acetic anhydride solution. Thebenzopyrylium salt has an active methyl or methylene radical.

In the case of Equation B, 2-[(4'-benzopyranylidene)-methylJbenzopyrylium derivative (V) is obtained by an addition reactionof 4-methoxybenzopyrylium o-nitrobenzene sulfonate (I) with abenzopyrylium salt (IV) in an acetic anhydride solution. Thebenzopyrylium salt has an active methyl radical.

EQUATION A anion- I anion- R1 \/-R| R3 R1 iH, %-R4 (III) EQUATION B O X4, on, R,

auionanion- R5 R3 R1 Rs YE- 8 9 TABLE lcontinued Compound number: Nameof Compound 1 13. 2- (2-p-methoxystyryl-3',6'-diphenyl-4'-benzopyranylidene) methyl] -3-phenylbenzopyryliumperchlorate 2- (2'-3 ",4"-dimethoxystyryl-3 ,6-diphenyl-4'-benzopyranylidene methyl] 3-phenylb enzopyrylium perchlorate 2-(2-p-methoxystyryl-3'-phenyl-6'-methyl-4'- benzopyranylidene) methyl]benzopyrylium perchlorate 2-[ (2'-p-methoxystyryl-3 '-phenyl-6'-methyl-4'- benzopyranylidene) methyl] -3-pheny1benzopyryliumperchlorate 2- (2'-3 ",4"-dimethoxystyryl-3 '-pheny1-6'-methyl-4'-benzopyranylidene) methyl] benzopyrylium perchlorate 2-[ (2'-3,4"-dimethoxystyryl-3-phenyl-6'-methyl- 4--benzopyranylidene)methyl]-3-phenylbenzopyrylium perchlorate 2- (2'-p-furyl( a ethenyl-3'-phenyl-6'-methyl-4- benzopyranylidene )methyl] benzopyryliumperchlorate 2-[ (2'-B-furyl (11 ethenyl-3'-phenyl-6 -methyl-4'-benzopyranylidene) methyl] -3-phenylbenzopyrylium perchlorate 2-[(2'-phenyl-4'-benzothiopyranylidene) methyl] benzopyrylium perchlorate2- 2'-phenyl-4'-b enzothiopyr-anylidene) methyl]- B-phenylbenzopyryliumperchlorate 2-[ (2'-phenyl-4'-benzopyranylidene) methyl]-4-pmethoxyphenylbenzothiopyrylium perchlorate 2-2-phenyl-4'-benzopyranylidene) methyl] -3-phenyl-4-p-methoxyphenylbenzopyrylium perchlorate 2-(2-a-phenyl-p-rnethoxystyry1-4'-benzopyranylidene methyl]-4-p-methoxyphenylbenzothiopyrylium perchlorate 2-(2-a-phenyl-p-methoxystyryl-4'-b enzopyranylidene methyl]-3-phenyl-4-p-methoxyphenylbenzothiopyrylium perchlorate 2-[(2'-phenyl-4-benzothi0pyrany1idene methyl]4-p-methoxyphenylbenzothiopyrylium perchlorate 2-[(2'-pheny1-4'-benzothiopyranylidene methyl]3-phenyl-4-p-methoxyphenylbenzothiopyrylium perchlorate Table 2 listsadditional information on the absorption maximum in dichloroethane andmelting point of the novel compounds according to the invention.

TABLE 2 Absorption maximum in dichloroethane (m 415 and 710. 430 and720. 410 and 630. 635

490 and 575. 575 and 660. 500 and 610. 490 and 670. 157160 550 and 670.103-105 610.

430 and 700. 420 and 730. 420 and 650. 500 and 600. 495 and 710. 135440580.

555. 420 and 730. 415 and 730. 410 and 700. 500 and 600. 485. 170-175505.

Compound number TABLE 2--Continued Compound number Melting pointvAbsorption maximum in dichloroethane (my) 560. 500 and 590.

- 660 and 710.

410 and 650. 430 and 690. 420 and 700.

1 550 and 650.

59 495 and 600 610, 650 and 700. 415 and 650.

1 425 and 700.

415 and 730. 660.

540 and 600. 660 and 710. 580 and 720. 415 and 720. 425 and 720.

0. 490 and 580. 600 and 720. 610 and 660. 480 and 740. 495 and 580. 590and 700. 550 and 750. 420 and 680. 555 and 680.

570. 585 and 690. 570.

530 and 690.

- 590. 500 and 600.

570 and 760. 495

65051111 700. 500 and 710.

590. 495 and 640. 550. 415 and 720.

640 and 700.

410 and 745. 425 and 730.

600 and 680. 600 and 720. 550 and 700. 650 and 695.

500 and 610.

500 and 610.

500 and 610.

575 and 675. 575 and 675. 575 and 675.

620 and 690.

525 and 560.

630 and 690.

610 and 690.

' 580111111 690. 565 and 620. 550 and 635.

570 and 610. 570 and 610.

. 570 and 610. 580 and 630.

600 and 645.

' 570 and 620.

600. 665 and 600.

. 570 and 610.

590. 565 and 605.

615 and 675.

' 559 and e57.

589 and 663. 656. 660.

12 The following description will explain a practical (b) 2 (a phenyl pmethoxystyryl) 4 [(2'-phenylmethod for makingbenzopyranylidene-methylbenzo- 4 benzopyranylidene)methyl]benzopyryliurnperpyrylium salts or benzothiopyranylidene-methylbenzochlorate (compoundnumber 7) (Lee.

Q g C10;

pyrylium salts with reference to exemplary compounds. 5 .5 grams of 2 (aphenyl p methoxystyryl)-4methyl- The details of the preparation of othercompounds will be benzopyrylium perchlorate and 5.5 grams of 2-phenyl4-apparent to the skilled in the art from the precedingdismethoxybenzopyrylium o-nitrobenzene sulfonate are disclosure and thefollowing illustrative examples of prepasolved in 150 milliliters ofacetic anhydride to a solution. ration methods of various compoundsaccording to the The solution is then refluxed for 15 minutes and pouredinvention: into 900 millilters of 10 weight percent p-erchloric acid.

The solution is filtered to obtain a precipitate. The pre- (a)2-phenyl-4-[(2'-phenyl-4'-benzopy yl den y l cipitate is reprecipitatedwith dichloroethane ether. Prebenzopyrylium perchlorate (compoundnumber 1) cipitated crystals are filtered 01f, washed with ether and Q QAW ,0 Q tl. g are 5.5 grams of 2-phenyl-4-methoxybenzopyryliumo-nitrodried to obtain 5.5 grams (theoretical yield 69%) of benzenesulfonate, which is obtained from flavone and blue crystals havingmelting Point of to methyl omitmbenzenesulfonate, and 5 grams of 2pheny1 In the procedure above mentioned the solution is poured into anether solution of B=F -O(C H instead of 10 4-benzylbenzopyryl1umperchlorate are dlssolved 1n 150 weight percent perchloric acid. In hicase z-(u-phenyl-pmilliliters of acetic anhydride to a solution. Thesolution methoxystyryl) 4 [(2, phenyl benzopyranylidene) is thenrefluxed for 15 minutes and poured into 900 millimethyl]benzopyryliumfluoroborate (compound number liters of 10 weight percent perchloricacid. The solution is Obtained- In the Procedllffi When the So ution isis filtered to obtain a precipitate. The precipitate is dried Pour? intoa 10 Weight Percent Zinc chloride aqueous solutlon, 2 (orphenyl-p-methoxystyryl)-4-[(2'-phenyland dissolved again n drchloroethanto a solution. For benzopyranylidene)methyl]benzopyrylium Chlormpurrficatlon the solution is poured into ether. Precipitated 5 Zincate(compound number 90) is obtained crystals are filtered off, washed wrthether and drred to (c) 2 p methoxystyryl 3 Obtaln 4 grams (theoretlcalYleld of green crystals benzopyranylidene)methyl] 6 methylbenzopyryliumhaving a melting point of to 139 C. perchlorate (compound number 18) 2styryl 4 methoxybenzopyrylium o nitrobenzenesulfonate (melting point,155 to 157 C.) is obtained by a reaction of 2-styrylchromone and methylo-nitrobenzenesulfonate in dry benzene at 50 C. for 24 hours. Accordingto the same reaction as shown in procedure (a), 2 styryl 4methoxybenzopyrylium o nitrobenzenesulfonate reacts with2-p-methoxystyryl-3-phenyl-4,6-dimethylbenzopyrylium perchlorate toobtain 2-p-methoxystyryl 3 phenyl 4 [(2 styryl-4'-benzopyranylidene)methyl] 6 methylbenzopyrylium perchlorate crystals which have a color ofreddish violet in dichloroethane and have a melting point of 159 to 162C. The product is obtained in 73% yield.

(d) 2 (a phenyl pmethoxystyryl)-4-[(4'-benzopyranylidene)methyl]benzopyrylium perchlorate(compound number 22) 4 methoxybenzopyrylium o nitrobenzenesulfonatereacts with 2 (a phenyl p methoxystyryl)-4-rnethyl] benzopyryliumperchlorate to 2 (a phenyl p methoxystyryl) 4[(4-benzopyranylidene)methyH-benzopyrylium perchlorate in the sameprocedure as the procedure (a). The crystals have a color of violet indichloroethane and a melting point of 174 to 178 C. The prodnet isobtained in 95% yield.

(e) 2 p methoxystyryl 4 [(2 3",4 dimethoxystyryl 4benzopyranylidene)methyHbenzopyrylium perchlorate (compound number 42)OOH: NO:

2-(3,4' dirnethoxystyryl) 4 methoxybenzopyrylium o-nitrobenzenesulfonate(melting point 211 to 213 C.) is obtained from a reaction of2-(3',4'dimethoxystyryl) chromone and methyl o-nitrobenzene sulfonate.6.5 grams of 2 (3,4 dimethoxystyryl)-4-methoxybenzopyryliumo-nitrobenzenesulfonate and 4.5 grams of2-p-methoxystyryl-4-methylbenzopyrylium perchlorate are dissolved inmilliliters of acetic anhydride to a solution. The solution is heated at100 C. for 100 minutes. After cooling the solution is poured into 900milliliters of 10 weight percent perchloric acid. Precipitates arefiltered oif and dried. For purification, reprecipitation is made usingdichloroethane and ether. 3.2 grams of product is obtained in 41% yield.The product has a color of dark violet in dichloroethane and a meltingpoint of to 181 C.

C10 r Ha 2-phenyl-4-methoxybenzothiopyrylium o-nitrobenzenesulfonate isobtained from thioflavone and methyl o-nitrobenzenesulfonate. As thesame procedure as procedure r (e), the product is obtained in 62% yield.The product has a color of reddish violet in dichloroethane and meltingpoint of 170 to 177 C.

(h) 2 [(2 phenyl 4' benzopyranylidene)methyl]-3- phenylbenzopyryliumperchlorate (compound number 60 16 Q OH=CH-OOH: h to CH Q @a =CH-OCH15.5 grams of 2 phenyl 4 methoxybenzopyrylium o-nitrobenzenesulfonate,which is obtained from flavone and methyl o-nitrobenzenesulfonate, and 4grams of 2-methyl-3-phenylbenzopyry1ium perchlorate are dissolved in 150milliliters of acetic anhydride to a solution. The solution is heated at100 C. for 15 minutes. After cooling the solution is poured into 900milliliters of 10 weight percent perchloric acid. Precipitated productis filtered ofi and dried. For purification, reprecipitation is madeusing dichloroethane and ether. The product has a color of blue indichloroethane and a melting point of OCHa 128 to 134 C. The productyields 3 grams (theoretical yield 46%). Compound number 93 (fiuoborate),compound number 94 (chloroferrate) or compound number 95 (nitrate) isobtained using either solution of borontrifluoride etherate, aqueoussolution of ferric chloride or diluted nitric acid respectively insteadof 10 weight percent perchloriic acid.

. C10 HE C 10 4 OCH;

2 (a-phenyl-p-methoxystyryl) 4 methoxybenzopyryliumo-nitrobenzenesulfonate, which is obtained from 2 (a phenyl pmethoxystyryl)chromone and methyl o-nitrobenzenesulfonate, reacts with2-methyl-3-phenylbenzopyrylium perchlorate in the same procedure asprocedure (h). The reaction product yields in 43%. The product has acolor of violet in dichloroethane and a melting point of 158 to 163 C.

It has been discovered according to the invention the compounds listedin Table 1 are sensitizing agents which can improve thephotoconductivity and the spectrum characteristics of photoconductivepolymeric compounds such as poly-N-vinylcarbazole, brominatedpoly-N-vinylcarbazoles, polyacenaphthylene, etc. These polymers, exceptbrominated poly-N-vinylcarbazoles, are prepared in a per se well knownmethod. The brominated poly-N-vinylcarbazole can be prepared by thefollowing method: To the solution of grams of poly-N-vinylcarbazole in450 milliliters of chlorobenzene, there are added 18.44 grams of-N-bromosuccinimide and 0.173 gram of benzoyl peroxide. The mixture isheated at 80 C. for 2 hours while being stirred thoroughly and is pouredinto methanol to obtain a white polymer. The polymer is dissolved inchlorobenzene and again poured into methanol for purification. The purepolymer thus obtained as a precipitate exhibits upon elementary analysisa halogen content of 29.87 weight percent which approximates the valuecalculated, i.e. 29.44 weight percent of the monobromosubstitutedproduct from poly-N-vinylcarbazole. This indicates that the polymerobtained is a monobromosubstituted product. The degree of brominationvaries from 50 mole percent to 200 mole percent according to reactionconditions.

The novel sensitizer comprising at least one compound from the grouplisted in Table 1 is dissolved in a suitable solvent, such asdichloroethane, methylene chloride, chloroform, or a combinationthereof, and is added to the solution of the photoconductive polymerdescribed above. The preferable amount of the sensitizer added is from0.01 to 3.0 weight parts in connection with 100 weight parts of thephotoconductive polymer. Advantageously, the amount thereof is from 0.1to 2.0 weight parts in connection with 100 weight parts of thephotoconductive polymer.

For the preparation of the photoconductive insulating layer, a saidsolution of the photoconductive polymer and the sensitizer in a suitablesolvent is applied to the elec- 18 troconductive support in per se usualmanner, for example, by spraying, by means of bladed coating, by meansof whirler coating, etc., and then dried so as to produce 0 o=cn -oom cm11102 a homogeneous photoconductive insulating layer on theelectroconductive support. Operable solvents are benzene, toluene,chlorobenzene, dioxane, methylene chloride, dichloroethane andcombinations thereof. Said solution may be incorporated with suitableplasticizers and/or organic colloids for improving the flexibility andstrength of the photoconductive polymer. Operable plasticizers are asfollows: chlorinated diphenyl, dimethyl phthalate, diethyl phthalate andoctyl phthalate. Operable organic colloids are as follows: natural andsynthetic resins, e.g. phenol resin, phenol resin modified with resin,polyvinyl acetal, polyvinyl butyral, polyvinyl cinnamate, polycarbonateresin. Operable materials for electroconductive supports may be made ofany materials which satisfy the requirement of the electrophotographicart, e.g. metal plate or glass plate having NESA coating, plate or foilmade of electrically conductive resin or coated with evaporated thinmetal layer. If paper is to be used as a support for the photoconductivelayer, pretreatment of the paper against penetration of the coatingsolution is advisable. The transparent support can produce a transparentelectrophotographic plate, foil or film. After an electrostatic chargehas been applied, i.e. after the layer has been charged positively ornegatively by means of a corona discharge, the layer becomes lightsensitive.

The reproducton of images by the electrophotographic method is carriedout as follows: when the photoconductive layer has been charged by meansof a corona discharge apparatus, the support with the sensitized layeris exposed to light under a master and is then dusted over in a per seknown manner with a resin powder colored with carbon black. The imagethat now becomes visible can easily be wiped off. It can also be fixedby heating at about C. From positive masters, positive imagescharacterized by good contrast are produced.

This invention is still further illustrated with reference to thefollowing illustrative examples.

EXAMPLE 1 1 gram of polyacenaphthylene and 0.6 gram of, as aplasticiser, chlorinated diphenyl (commercially available as Kanechlor),are dissolved in 8 milliliters of chlorobenzene. To the solution areadded 0.5 milliliter of dichloroethane containing 0.006 gram of asensitizer corresponding to compound number listed in Table 1. Thesolution is applied to an aluminum plate by means of whirler coating andis dried to form a layer of 7,111 in thickness. After said aluminumplate provided with the layer is charged negatively by means of coronadischarge with a charging device maintained at approximately 6000 voltsin the dark, it is placed under a positive master and is exposed to a100 w. tungsten lamp at an illumination of 50 luxes, and the said plateis powdered over with a developer in a per se known manner. Thisdeveloper consists of toner and carrier. The toner consists of lowmelting point polystyrene, colophony and carbon black. The toner ismixed with a carrier substance such that the toner becomestriboelectrically charged with a charge opposite to that produced on theplate. A positive image is produced and is fixed by slight heating. InTable 2, there are shown the optimum amounts of exposure in lux-secondunits.

TABLE 2 Compound number: Optimum exposure (lux-sec.) None 200000 EXAMPLE2 1 gram of poly-N-vinylcarbazole, chlorinated diphenyl (commerciallyavailable as Kanechlor) and 0.006 gram of a sensitizer, corresponding tocompound number listed in Table 1, in milliliters of dichloroethane to asolution. The solution is applied to an aluminum plate by means of bladecoating and is dried to form a layer of 10 in thickness. Anelectrophotographic image is produced in the same way as that describedin Example 1. In Table 3, there are shown the optimum amounts ofexposure in lux-second units to produce exactly the original images.

TABLE 3 Compound number: Optimum exposure (lux-sec.) None 20000 1 50 2220 3 60 4 70 5 2'2 6 44 7 26 8 62 9 44 10 48 l l l 60 12 220 20 TABLE3Continued Compound number: Optimum exposure (lux-sec.)

21 TABLE 3'-Conti uued Compound number: Optimum exposure (lux-sec.)

It is clear from Table 3 that the novel sensitizers improve thephotoconductivity of poly-N-vinylcarbazole.

EXAMPLE 3 1 gram of brominated poly-N-vinylcarbazole(monobromo-substituted product), 0.5 gram of polycarbonate resin(commercially available as Panlite-C), 0.3 gram of chlorinated diphenyl(commercially available as Kanechlor) and 0.002 gram of sensitizerlisted in Table 1 are dissolved in a mixed-solvent of 8 milliliters ofchlorobenzene and 2 milliliters of dichloroethane. This solution isapplied to an aluminum plate by means of a blade coating and dried toform a layer of 14 2 in thickness. On this support, electrophotographicimages are produced in the same way as that described in Example 1.Table 4 shows the optimum amounts of exposure in lux-second units toreproduce exactly the original images.

TABLE 4 Compound number: Optimum exposure (lux-sec.)

None 800 TABLE 4Continued Compound number:

Optimum exposure (lllX-SEC.)

TABLE 4-Continued Compound number: Optimum exposure (lux-sec.)

It is clear from Table 4 and FIGS. 1 to 9 that the novel sensitizersimprove the photoconductivity and the spectrum characteristics ofbrominated poly-N-vinylcarbazole.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will he understood that variationsand modifications can be efiected Within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

What we claim is:

1. A11 electrophotographic material comprising a conductive supportlayer and photoconductive insulating layer, the latter comprising acombination of a photoconductive polymeric compound and a sensitizingamount of a sensitizer having the following formula:

anion- R is hydrogen, phenyl or an ethenyl radical selected from thegroup consisting of styryl, p-methoxystyryl, 3,4-dimethoxy-styryl,a-phenylstyryl, 0a phenyl pmethoxystyryl, fl-furyl (a)ethenyl anda-phenyl-fl tfuryl(a) ethenyl;

R is hydrogen or phenyl;

R is hydrogen, methyl or phenyl;

R is hydrogen or phenyl;

R is hydrogen, phenyl or an ethenyl radical selected from the groupconsisting of styryl, p-methoxystyryl, 3,4-dimethoxy-styryl,a-phenyl-p-methoxystyryl, flfuryl(u')ethenyl anda-phenyl-p-turyl(a')ethenyl;

R is hydrogen or phenyl;

R is hydrogen or phenyl;

the anion is an anionic function selected from the group consisting ofperchlorate, fluoroborate, chloroferrate, chlorozincate and nitrate; and

X is oxygen or a sulfur atom;

said photoconductive polymeric compound comprising at least one compoundselected from the group consisting of poly-N-vinylcarbazole, brominatedpoly-1 vinylcarbazole and polyacenaphthylene.

2. An electrophotographic material according to claim 1, wherein saidsensitizer comprises at least one compound selected from the groupconsisting of 2- a-phenyl-p-methoxystryl) -4-2-phenyl-4'benzopyranylidene)methyl] benzopyrylium perchlorate,

2-p-methoxystyryl-4-[ (2'-3",4"-dimeth0xystryl-3'-phenyl-6'-methyl-4'-benzopyranylidene)methyl]benzopyrylium perchlorate,

2-[ (2'-phenyl-4'-benzopyranylidene methyl] -3-phenyl benzopyryliumfiuoroborate,

2- (2'-phenyl-4'-benzopyranylidene methyl] -4-p-methoxyphenylbenzothiopyrylium perchlorate, and

2-[ (2-phenyl-4'-benzothiopyranylidene methyl] -4-pmethoxyphenylbenzothiopyrylium perchlorate.

3. An electrophotographic material accordingto claim 1, wherein saidcombination comprises Weight parts of photoconductive polymeric compoundand 0.01 to 3.0 weight parts of sensitizer.

References Cited UNITED STATES PATENTS 3,617,268 11/1971 Murakarni eta1. 96-1.5 3,526,502 9/1970 M-urakami et al. 96-1.6 X 3,586,500 6/1971Contois et al 961.6

CHARLES E. VAN HORN, Primary Examiner US. Cl. X.R. 260327 R, 345.2

